Interface Engineering Boosting High Power Density and Conversion Efficiency in Mg₂Sn_0.75Ge_0.25‐Based Thermoelectric Devices

Abstract

Electrode contact interfaces for practical thermoelectric (TE) devices require high bonding strength, low specific contact resistivity, and superb stability. Herein, the state‐of‐the‐art Cu2MgFe/Mg2Sn0.75Ge0.25 interface is designed for Mg2Sn0.75Ge0.25‐based TE devices, adhering to the general strategy of high bonding propensity, thermal expansion matching, diffusion passivation, and dopant inactivation. The interfacial stability is verified by the in situ transmission electron microscopy analysis, thereby confirming the contributions from decreasing the chemical potential gradient and increasing the diffusion activation energy barrier. The single‐leg device exhibits a high power density (ωmax) of 2.6 W cm−2 and conversion efficiency (ηmax) of 8% under a temperature difference (ΔT) of 370 °C, which is the record‐breaking value in comparison to other Mg2(Si, Ge, Sn)‐based TE devices. Additionally, a two‐couple device with p‐type Bi2Te3 shows an excellent ωmax of 1.3 W cm−2 and ηmax of 5.4% under a ΔT of 270 °C, comparable to commercial Bi2Te3 devices. The proposed interface design strategy provides a general technique for constructing high‐performance devices using cutting‐edge TE materials.

A high performance eco-friendly MgAgSb-based thermoelectric power generation device near phase transition temperatures

“…The order of magnitude of k is 10 −3 , indicating an exceptional interfacial operating lifespan. 21 To the best of our knowledge, this is the first dataset for evaluating interfacial strength stability in the MgAgSb-based TE system that has been publicly published.…”

“…Significant efforts have been made in the quest for Te-free TE devices. 14 For example, Bi 2 S 3 , 15 MgAgSb, 16–18 Mg 3 Sb 2 , 19 CdSb, 3 PbSe, 20 Mg 2 Sn, 21 skutterudite (SKD), 22 SnSe, 23 and half-Heusler alloy 24 have flourished in recent years. Among these, eco-friendly Mg-based p-type MgAgSb and n-type Mg 3 Sb 2 thermoelectrics have shown ZT values comparable to commercial Bi 2 Te 3 near the low-grade temperature range (Fig.…”

Recent advances of 2D conductive metal–organic frameworks in thermoelectrics

“…37–46 Big progress has been achieved in inorganic TE materials in the past years. 47–64 He et al enhanced the ZT to 2.7 at 750 K in germanium telluride-based high-entropy materials and realized a high experimental conversion efficiency of 13.3% by high-entropy concept tuning electron and phonon decoupling. 53 Zhao and coworkers developed a lattice plainification strategy for defect engineering to weaken defect scattering and boost carrier mobility, leading to a ZT of ∼1.5 at 300 K. 54 However, traditional inorganic TE materials are often composed of transition metals, such as Pb, Te, Bi, etc.…”

Low-Cost Magnesium-Based Thermoelectric Materials: Progress, Challenges, and Enhancements

“…The CTE (22.1 × 10 −6 K −1 ) of the Cu-based ternary alloy, Cu 2 MgFe, was closer to that of Mg 2 Sn 0.75 Ge 0.25 (20.6 × 10 −6 K −1 ) compared to Cu, Mg (29.5 × 10 −6 K −1 ), and Fe (16.0 × 10 −6 K −1 ), resulting in a high bonding strength of 15.1 MPa and a low contact resistance of 1.6 × 10 −5 Ω•cm 2 for a special designed Cu 2 MgFe/ Mg 2 Sn 0.75 Ge 0.25 interface. 142 The stable interface was strengthened by reducing the chemical potential gradient and improving the diffusion activation energy barrier.…”

“…Lower interfacial resistance of multielement alloys, such as (Co, Cr, Ti)Si 2 , Ni 45 Cu 55 , 304 stainless steel (304SS), and Mg 2 SiNi 3 , have also been reported. 142 4. 3 148 The adhesion of the sputtering deposited Cu film electrodes with a postannealing treatment showed the best adhesion performance and lower contact resistance than that of the Ni and Au layers.…”